hello-algo/codes/python/chapter_heap/top_k.py

"""
File: top_k.py
Created Time: 2023-06-10
Author: krahets (krahets@163.com)
"""

import sys
from pathlib import Path

sys.path.append(str(Path(__file__).parent.parent))
from modules import print_heap

import heapq


def top_k_heap(nums: list[int], k: int) -> list[int]:
    """基于堆查找数组中最大的 k 个元素"""
    # 初始化小顶堆
    heap = []
    # 将数组的前 k 个元素入堆
    for i in range(k):
        heapq.heappush(heap, nums[i])
    # 从第 k+1 个元素开始，保持堆的长度为 k
    for i in range(k, len(nums)):
        # 若当前元素大于堆顶元素，则将堆顶元素出堆、当前元素入堆
        if nums[i] > heap[0]:
            heapq.heappop(heap)
            heapq.heappush(heap, nums[i])
    return heap


"""Driver Code"""
if __name__ == "__main__":
    nums = [1, 7, 6, 3, 2]
    k = 3

    res = top_k_heap(nums, k)
    print(f"最大的 {k} 个元素为")
    print_heap(res)